The present invention relates to ozone processing and, in particular, to an ozone processing monitor which can be used in ozone processing to determine whether sufficient ozone treatment has occurred on a production part needing ozone treatment. Specifically, the ozone processing monitor of the present invention comprises an ozone sensitive material which is capable of producing a visual color change upon exposure to ozone. In one embodiment, the ozone sensitive material employed in the present invention is capable of forming a surface oxide layer upon exposure to ozone that produces a visible color change in the ozone sensitive material which can be used in determining if too little, too much or appropriate ozone treatment is occurring. In another embodiment of the present invention, the ozone sensitive material is an organic material that oxidizes and consequently thins during ozone treatment. In yet another embodiment, the ozone sensitive material is a chromophoric compound such as a dye that bleaches during exposure to ozone.
The ozone processing monitor of the present invention represents an advancement over prior art ozone processing monitors since it is evaluated during or following the actual ozone processing, i.e. real time basis, not several processing steps later as is required by prior art ozone monitors. The present invention also provides a method of using the inventive ozone processing monitor during or following ozone processing to determine whether sufficient ozone treatment has occurred. The monitor of the present invention can also be used to determine chamber uniformity, chamber to chamber variations, or process variables such as time, pressure, temperature or concentration.
In semiconductor lead-on-chip (LOC) memory packaging, ozone is used to alter the surface of the polymeric adhesive of the die attach tape in a manner which enhances adhesion between the polymeric adhesive and the mold compound. A major problem in this area has been the lack of an ozone processing monitor that indicates the health of the ozone process on a real time basis. Traditionally, acoustical scanning of the molded product is performed several process steps after ozone treatment to determine effectiveness of the ozonation as evidenced by delamination within the final package.
This prior art technique suffers because the process time between ozone and the molding operation allows a significant amount of the product to be built defective. That is, products exhibiting delamination can pass final testing but fail at a later date; therefore product lots exhibiting delamination must be discarded or 100% acoustically scanned to identify and remove the defective parts.
Moreover, post ozone delamination has been found to be caused by either adhesive failure at the mold compound/tape adhesive interface or cohesive failure within the tape adhesive. It has been determined that adhesive failure results from insufficient ozone treatment, whereas cohesive failure is caused by excessive ozonation. The failure mode of the delamination must be determined by a time consuming cross sectional technique resulting in extensive down time of the ozone operation while the failure mechanism is determined.
Although the prior art discloses many different types of flow-through ozone monitors such as described, for example, in U.S. Pat. Nos. 5,185,129 to Koutrakis, et al. and 5,052,382 to Wainwright, there still exists a need for developing a new and improved ozone monitor which is not an ozone concentration monitor but an ozone reaction monitor for a process. That is, there is a need for providing an ozone monitor which provides information regarding the ozone process effectiveness on a real time basis, not several processing steps after the product is formed, as is required in typical prior art ozone processing. Moreover, there is a need for providing an ozone processing monitor which can differentiate between too little and excessive ozone treatment such that, if either is detected, the malfunctioning ozone chamber or process can be stopped and the processing reaction conditions readjusted or chamber repaired so as to provide effective ozone treatment to a production part.
One object of the present invention is to provide an ozone processing monitor which can be employed on a real time basis to monitor whether sufficient ozone treatment has occurred on a production part needing such treatment.
Another object of the present invention is to provide an ozone processing monitor which is easy to use and which can readily differentiate between too little, too much or appropriate ozone treatment.
A further object of the present invention relates to an ozone processing monitor which provides a visible change in the monitor material that correlates to the ozone reaction on the production part and thus can be used to initiate and regulate changes in the ozone processing conditions.
A yet further object of the present invention is to provide an ozone processing monitor which adds no significant cost to the operation and which can be used without contaminating the production part being processed.
These as well as other objects and advantages are achieved in the present invention by utilizing an ozone processing monitor comprising an ozone sensitive material which is capable of undergoing a physical or chemical change upon exposure to ozone, wherein said physical or chemical change produces a visible color change of said ozone sensitive material which can be monitored during, or evaluated after, ozone processing.
The term xe2x80x9cphysical or chemical changexe2x80x9d is used herein to denote that upon exposure to ozone the appearance of the ozone sensitive material is sufficiently altered so as to provide a visible color change in the material. This can be obtained in the present invention, for example, by thinning, bleaching or forming an oxide layer in the ozone sensitive material. Since the color change is directly proportional to the reaction of ozone, the monitor of the present invention is a viable means for determining if too much, too little or appropriate ozone treatment has occurred within the chamber or on a production part needing ozone treatment.
As stated above, the ozone sensitive material employed in the present invention is a material which is capable of undergoing a physical or chemical change, e.g. forming an oxide layer, thinning or bleaching, upon exposure to ozone. Any of the foregoing produces a visible color change in the ozone sensitive material that can be used in the present invention as a reaction monitor for ozone processing.
Another aspect of the present invention relates to a method of using the above described ozone processing monitor to determine whether sufficient ozone treatment has occurred on a production part. In accordance with this aspect of the present invention, the method comprises the steps of:
(a) providing a production part requiring ozone treatment and an ozone sensitive material which is capable of undergoing a physical or chemical change upon exposure to ozone into an ozone processing reactor chamber, wherein said physical or chemical change produces a color change of said ozone sensitive material which can be monitored during or following ozone processing;
(b) introducing ozone into said reactor chamber; and
(c) monitoring the color change of the ozone sensitive material and comparing the same to standards of the same ozone sensitive material, wherein said standards have been previously treated with ozone under various reaction conditions so as to provide a spectrum of colors which can be employed to determine whether sufficient ozone treatment has occurred on said production part.
In accordance with the method of the present invention, the ozone treatment may be stopped at any time during the operation if the color of the ozone processing monitor is below a minimum threshold or above a maximum threshold. This can be easily done in the method of the present invention by comparing the ozone processing monitor to the standards having a spectrum of color associated therewith which corresponds to various levels of ozone treatment.
The present invention also provides a method of monitoring the uniformity and effectiveness of an ozone reactor system. In accordance with this aspect of the present invention, an ozone sensitive material as described hereinabove is introduced into an ozone reactor chamber, exposed to ozone and thereafter evaluated by comparing the exposed ozone sensitive material to standards that were previously reacted with ozone over a range of process parameters such as time, pressure, temperature and ozone concentration.